The objective of this renewal proposal is the continued engineering and laboratory investigation of solid and microporous membranes as blood compatible materials. Our focus is on understanding and favorably altering the initial events in the interaction of blood components and polymer-based prosthetic devices. Specifically, we plan to study the initial adsorption, modification and desorption of protein at the polymer-solution interface. We will employ new, sensitive measurements of polymer microtopographical surface energy distribution and the microtopographical distribution of protein adsorbate, its mass and number density, employing partial gold decoration transmission electron microscopy (GDEM) and total internal reflectance-fluorescence (TIRF) for these purposes. TIRF will be modified to allow fluorescence depolarization measurements of molecule-polymer energy transfer and protein denaturation, to be correlated with protein adsorbate density. The effects on blood compatiblity of competitive protein adsorption, of environmental factors such as fluid shear, and the effects of surface modification, including smoothing, glow discharge polymerization and aliphatic halide binding intermediates, will be evaluated. Particular attention will be directed to the ability of preadsorbed albumin to inhibit subsequent adsorption of proteins implicated in coagulation and cell adhesion.